Welding system



H. J. GRAHAM Aug. 3, 1954 WELDING SYSTEM I 2 Sheets-Sheet 1 Original Filed Aug. 10, 1948 Ezra ffizaziaiiz t z W Aug. 3, 1954 H. J. GRAHAM 2,685,630

WELDING SYSTEM Original Filed Aug. 10, 1948 2 Sheets-Sheet 2 1?; I? a Z 5306 271? Eff f F 13 4/ h ax:

mzs.

Patented Aug. 3, 1954 WELDING SYSTEM Harold J. Graham, Highland Park, Mich, as-

signer to Graham Mano Detroit, Mich, a corpora Original application Au Divided and 12 Claims. 1

The present invention relates to electric welding sys"c-ms and-more particularly-to a welding method and to welding equipment of the type wherein a welding current impulse is applied simultaneously with a mechanical blow tending to unite the construction elements to be joined. This application is a division of my co-pending application Serial No. 43,498, filed August 10, 1948, now Patent No. asraess of August 15, 1-950, which is in part a continuation or application Serial No. 615,758, filed September 12, 1945, now Patent No. 2,46'2',37-9 of April 19, 1949.

It has heretofore been proposed (for example in United States Patent No. 1,066,468 to Chubb) to apply a percussive blow to two work pieces, for example while directing a welding current through the two pieces. However, these previously proposed systems require rather elaborate current timing, work holding, and blow applying mechanisms for correlating the mechanical and electrical energy impulses; in most instances such provisions are made necessary due to the fact that the work pieces are first brought into contact, whereupon an arc is drawn and thereaft r the percussion blow applied.

It is one of the rnain objects of the present invention to provide an extremely simple, rugged and yet reliable system for the application of a mechanical blow and an electric welding impulse to two work pieces to be joined by welding with welding apparatus of the type dealt with in my Patent No. 2,467,379.

In one of its principal aspects, the invention deals with the art of welding a rod or block shaped metal body (herein referred to as stud) to a surface intersecting the general direction of the stud, by providing one end of the stud with a substantially high resistance portion which offers a contact area considerably smaller than the cross sectional area of the stud by contacting this end portion with the surface to which the stud is to be welded, and by sending a current through the stud and the surf-ace while applying ther to pressure which as to intensity and time characteristic may vary between that exerted by a pneumatic tool and that applied as a percussive blow by a spring operated tool, whereby the high current density due to the reduced current carrying capacity of the narrow cross section at the contact portion imparts to the metal at that point a high temperature causing it to melt which instantaneous melting separates the end of the stud from the surface, eiiec-ting the formation of an are. This reduced tip portion of the stud may be constituted by a factoring Corporation, tion of Michigan gust 19, 1948, Serial No.

this application October 26, 1949, Serial No. 123,715

wedge "shaped 'or circular edge, a point, 'or simply an uneven end such as a clipped on end surface or, instead of shaping the end of the stud as indicated above, it might be reduced in cross sec tions through appreciable length for the same purpose, namely to cause initial flow of current sutliciently r gh to melt the material of the stud end so as initially to distance the stud and work piece not only to facilitate arc formation by ionizing and concomitantly widening the gap between stud and work piece but also by melting work pieces.

In another aspect, the invention is concerned with the configuration of studs for carrying out above indicated method of welding, such studs comprising according to the invention a smooth shank portion and a tip portion (herein also referred to as wire) extending in an axial "lir ction from the shank portion with a cross awa substantially smaller than that of the shanl: portion, the ratio of length to cross section of the tip portion or wire being selected to provide a current density suificient to melt the wire before the stud proper has reached the work piece. The cross sectional area of the wire tip should be substantially smaller than that of the shank portion, such that the ratio of length to cross section of this tip portion provides current density suiiicient to melt it during the time required by the stud to traverse the length of the tip wire when moved by a force surlicient to fuse the opposite surfaces of stud and work piece, melted by the arc that is initiated by the melting wire. Instead of using a single tip wire, several wires may be arranged at the tip of the depending upon the cross sectional area of the stud proper, as will be described more in detail hereinbelow. The above statements concerning the cross section and length of a single wire tip as analogously applicable to the combined cross sectional area of a multiwire tipped stud. Apparatus for welding in this manner with the work piece initially in mechanical contact is described in my Patent No. 2,461379.

in ocler to provide an inert atmosphere for the point of welding, there be pro ideal instead of the abovemientioned gas developing head a duct associated with the tool holder or a spacer, or separately extending towards the welding area, through which an inert gas can be supplied to the gap between work piece and stud; this gas supply is controlled by instrumentalities correlated with the actuator for the percussion tool or by that tool itself, such as the hammer or the stud carrying element. Apparatus of this 3 type is dealt with more specifically in my copending application Serial No. 81,130, now Patent No. 2,610,278, dated September 9, 1952.

These and other objects, aspects and features appear in the following description of several typical practical embodiments illustrating the novel characteristics of my invention. This description refers to drawings in which Fig. 1 is a longitudinal axial section through a welding hammer according to my invention;

Fig. 2 is a side elevation from the right hand side of Fig. 1;

Fig. 3 is a section on line 3-3 of Fig. 1;

Fig. 4 is a circuit diagram of a directcurrent supply system for welding apparatus according to the present invention;

Fig. 5 is a circuit diagram similar to Fig. 4, but for use with alternating current;

Figs. 6, 7 and 8 are diagrammatic sections through two work pieces undergoing a welding operation according to my invention;

Fig. 9 is a diagram schematically illustrating the use of a welding hammer according to Figs. 1 to 3, in a system according to Figs. 4 and 5;

Fig. 10 is an isometric view of a wedge shaped stud tip suitable for use with welding tools according to the invention; and

Fig. 11 is a longitudinal section of a cupped stud tip.

Referring to Figs. 1, 2 and 3, a welding hammer suitable for carrying out the invention will first be described.

In these figures, numeral H3 designates an outer guard and guide housing made from metal and carrying holding means, for example screwed thereto at H, a handle l2 which may tak the shape of a grip, or a round face fitting the palm of the hand, or any other shape which might seem convenient or suited for a particular purpose at hand. Such holding means might also be used for fastening the housing to a support or frame if mechanical instead of manual support should be desirable.

Slidingly fitting into the guide casing I6 is a plunger casing l5 made from insulating mate-- rial and having a groove l6 into which fits the key I? of a holding ring l8 screwed at E9 to the guide housing Ill.

Also secured to the guide housing ill, in the present instance by means of the screw ll holding handle 12, is a releasing block 21 made similar to casing l5 of insulating material, for instance Bakelite tubing and having a tubular extension 22 with a latch releasing rim 23. Held between the releasing block 2! and a spacer tube 24, likewise from insulating material, is a terminal block 25 made from metal and provided with a bore of two diameters, as indicated at 3! and 32. The outer larger bore 32 contains an insulating tube 33 whose inne diameter is that of the inner bore 31, and tube 33 and bore 3i hold a terminal piece 35 of metal which serves for holding a conductor (not shown in the drawing) by means of a contact screw 38. The insulating tube 35 is held in terminal block 25 by means of another set screw 39. The terminal block 25 also has a central bore 4| adapted for receiving a tail wire 42 held therein by means of a set screw 53. A reduced neck 46 of terminal block 25 is provided with a thread 41, for the purpose to be described hereinbelow.

Within the plunger casing 15 slides a plunger 5! having a somewhat raised impact and contact face 52 and a hollow portion 53. A second terminal block 55 fits into the hollow portion of block 5! wherein it is held by means of set screws 55. The outer larger portion of terminal block is provided with a thread 51, similar to thread 47 of terminal block 25. Block 55 is further provided with a conductor receiving bore El and a conductor holding screw 53, similar to the corresponding elements M and 43 of terminal block 25.

A resetting spring H is inserted between the inside of guide casing l5 and the outside of releasing block portion 22; this spring is substantially untensioned with the hammer in inoperative position as shown in Fig. 1 when it rests between the shoulder 21 of block 2! and the end face 28 of casing 15.

A second working spring 12 is fastened to blocks 25 and 55 by engaging it on threads 5? and 57; as will be described hereinbelow, this spring changes during the operation of the hammer from tensioned to compressed condition of stress.

The terminal block 55 is related to the recess 5i of tube I5 by means of a latch device which consists of a number, for example two spring latches 85 which tend to engage the annular shoulder 81 of tube I5 with their retaining faces 56. As indicated in Figs. 1 and 3, the latch springs 85 are fastened in slots 8? of block 5i, for example by means of rivets 88. The inclined faces of the latch springs 85, indicated at 89, are so arranged that during operation of the welding hammer, they are engaged by the inner rim edge of tube 2 l, indicated in Fig. 1 at 9i, so that upon contact with rim 9!, they are pressed inwardly into releasing position.

The plunger casing l5 carries at its outer end a contact and. percussion block it! fastened thereto by means of a retaining ring I02 engaging at 153 a thread of tube l5, and separated from the contact or percussion block it! by an insulating washer 105 of elastic material. This washer not only insulates block lfil from ring 2'52, but also serves as a shock absorber, When the entire mass of blocks El, 55 and NH hits ring 12 and casing l5, washer Hi5 gives to a degree sufficient to absorb the shock and prevent movement of th hammer as a whole. The percussion block lill has a threaded screw extension Iii carrying a work holder H2, which in the present instance consists of a slotted spring tube adapted for receiving and frictionally holding a stud or wire. It will be evident that this simple work piece holder can be replaced by any chuck or similar construction element, depending on the welding job at hand.

Fig. 4 illustrates the use of a welding hammer constructed in the manner described above by way of illustration, with reference to Figs. 1 to 3.

In Fig. 4, numeral 258 denotes a welding hammer of the abov described type. It will be noted that one work piece, indicated at 25!, is inserted in holder H2 and held by means of handle i2 against the second work piece 252, which may be a structural element, as for example a steel floor, wall Or girder.

The hammer and the work pieces are connected in a direct current welding circuit as follows. The circuit receives energy from terminals or and b of a direct current source appropriate for the purpose for example a 220 volt industrial supply network. A voltage regulating resistor R is connected across the supply wires leading on one side through a current limiting resistor RI to output terminal 205 which is connected to the second work piece 252 for example by means of a flexible acasgeso conductor 296 and a clamp 201 -or similar in strum'entality. The other side of resistor R, is connected through an adjustable tap tor other suitable adjusting means, and through a current limiting resistor R2 to a terminal device 26 8, which, together with terminals -a,'-b and :2 E5 and the other-circuitelements, may be :mounted on a convenient switchboard -or power supply unit. Work piece 2% and terminal --2t5 may be grounded by conventional means, as indicated in Fig. 4. A capacitor -'C is connected between terminals 295 and 2128, 'for the purpose of storing electric energy supplied by network a, h, during the period when the welding hammer retains the welding circuit open, that is so long as contact faces 52 and 1 96 are separated from each other as shown in Fig. 1. A securely insulated flexible conductor 2% leads from terminal 283 to con nector elements :35, 42, 55, 6! of the hammer, as indicated in 1. type herein described by way 0f example, limiting resistors of together approximately 10 ohms :-a :capacitor of about 18,000 micro'farad were found to besatisfactory for welding iron wire to sheet steel material.

"If "it is desired to operate welding hammers according to the present invention from alternatingcurrent networks, an arrangement schematically indicated in Fig. 5 maybe used.

In Fig. 5, e and 7 are terminals provided for connection 01": .a standard alternatingcurrent supply line to the primary Lil of a transformer L, whose ssecon'd'ary m feeds into a rectifier network N through limiting resistors R! and R2. This rectifier network :may be of the conventional bridge type as indicated in Fig. 5, incorporating four rectifier :units The output terminals of the rectifier network N are connected to terminals and 2&3, which correspond to those indicated with similar numerals inIFig. 4. Termirial 2615 may besgrounded and is again connected to the workpiece 202, whereas terminal 298 is connected, through flexible conductor .209, to the hammer .260.

lhe above described weldin system according to the invention (operates as follows:

A'work piece 2.0:] ,ior example a stud of the type to lot-described hereinbelow with reference to'Fig. 6, :is inserted in work holder 2, and "manually held, by :means "of handle it 2, towards the second work piece 262 at the point where the two pieces are to be joined. Pressure is now applied such as to cause compression of springs H and '12, sliding .movement between tubes It and it, with the inarr wer portion 22 of tubular block 2! entering into the wider portion 82 of the plunger casing i5. When the rim portion 591 of tube 22 reaches the oblique latch faces 89, the latches 3 6 are pressed inwardly icausing detachment thereof and sudden releaseof'the plunger 51 which thereupon impacts with considerable force upon the contact block member 1'01. At the same time, electricrcontact isestablished between-faces "52 and I66, welding current being suppliedfrom terminal 258 (Figs. 4 and 5), through flexible conductor its, connector .35, block 25, tall wire '42, connector 12., and connector block 55; the circuit is completed through work holder H2, work pieces 26.! and 282, and; the connection from connector 282 to terminal 205, which may be accomplished by means of conductor 286, or .by way of ground.

The two work pieces 201 and 20.2 are .fi-rmly united by the simultaneous application of the weldin current-and the percussion blow. When pressure is released from hand-1e I2, block :5! is For a welding tool of the 1 to the arc effect indicated Fig. 7.

retracted by spring '12 which became compressed shortly before the impact, until latches 83 again engage the retaining f-ace 8 of tube 15-5. The spring "1 which was compressed together with spring assists in this retracting operation. With the latches engaged and sprin 12 relaxed, the hammer is again in normal condition, ready for withdraw/a1 from the workpiece 2E1! and for insertion of :a new work piece and repetition of the-above described-cycle-of operation.

It should be noted that separation of the work pieces for initiating the welding-operation is unnecessary and not contemplated; current flow prior to the contact of faces 52 and ['06 is impossible and it ceases with the separation or" these contact members. "I-o the besto'f my present knowledge, welding with apparatus of the above described type proceeds as follows.

The contact of work pieces 23! and 262 does not extend over the enti-re area common to both work: pieces, especially since the end of the loose piece is more or less ragged and usually has a chisel point due to the tool "-with which it was severed, such shears or cutters. In order to emphasize this condition, I sometimes prefer to use a pointed stud. During the initial stage of the welding act, the work pieces are in the condition schematically indicated in Fig. 6, and at that moment the current flows through a comparatively small cross section at the tip .228 of the stud, which will therefore become heated and melt off rapidlyjleading 'for a very short time (in the order of a millisecond) to the condition indicated in Fig. '7. At that instant, the mechanical contact between the two work pieces is effectively interrupted and the common region ionized so that an are 222 forms as indicated in Fig. "I, promoting the welding operation by fusth adjacent portions-of both work pieces. In the next instant, the two work "pieces are "forced even closer together and into each other by the blow, joining over a comparatively extensive area indicated in Fig. 8, where 2 25 designates the region permanently joined mainly by fusing due It will be evident that these stages will not be strictly separated but take place more or less jointly and inseparably; at any rate the two work pieces remain pressurably joined during the entire operation so far as the effect or the hammer is concerned, and the arc formation is due to the melting or the contact area of loweitective-cross section and hence high resistance rather than to a mechanical separation of the work pieces after a closed current path has been established therethrough.

The partic liar usefulness of a welding device according to the invention will be apparent with reference to 9, where 202 is again a metailic structural element, in this instance for example a ceiling or wall which is covered by insulating material 210 temporarily attached thereto, and required permanently to be affixed by metal-studs. In order to accomplish this operation, studs 2M, held in chuck N2 of the welding hammer 2333 according to the invention, are inserted through the insulation layer 216, approximately perpendicular to wall .2 82, until they touch it, whereupon with continued pressure against handle 12, the above described welding takes place, aifiXi-ng the stud 2M firmly to wall 2-02. The hammer is with drawn :and the operation repeated. Washers, disks, straps, or similar structural elements indicated at 2H, may thereupon be threaded over I studs 20%, and the latter bent over as indicated at N2 of Fig. 9, thus firmly and permanently fastening the insulation to the metallic wall.

Fig. 9 also indicates how the power supply unit, indicated at s and incorporating the circuit ele ments shown in Figs. 4- and 5 may best be applied to work of this type.

It is understood that any convenient work holding device, chuck, or other similar appliance can be used with welding tools according to the present invention.

I found that for many purposes, particularly also for welding aluminum work pieces, pointed or edged tips are preferable to blunt tips. Simple points such as shown in Figs. 1 and '1 are often sufficient, but particularly satisfactory results are obtained when the contact area is enlarged such as by extending the essentially point shaped tip according to Fig. '7 into a linear edge as shown at 3d! of Fig. 10, or by extending it still further in the shape of a cupped tip with circular edge as shown at 362 of Fig. 11. The larger contact area of tips according to Fig. and particularly Fig. 11 reduces the current density at the weld which is sometimes advantageous since certain metal sheets, for example of copper, tend to burn through instead of welding if the contact area is too small.

It should be understood that the present disclosure is for the purpose of illustration only and that this invention includes all modifications and equivalents which fall within the scope of the appended claims.

I claim:

1. In the art of welding a loose stud or wire to a comparatively larger surface, the method which comprises providing the stud with a substantially uneven end surface, pressing said end surface against said larger surface, and thereafter sending a current through said stud and said surface substantially simultaneously with applying thereto a percussive blow, whereby said current initially melts the region of the contacting surfaces whereupon an arc forms between the surfaces slightly separated and ionized by melting and said blow causes joining of said surfaces.

2. In the art of welding a stud or wire to a surface, the method which comprises shaping one end of the stud with a substantially uneven surface, contacting said end with said surface, and sending a current through said stud and said surface while applying thereto a percussive blow, said current initially melting the material of the contact area, thus separating the end from the surface and forming an arc whereupon said blow joins said surfaces.

3. In the art of welding a stud or wire to a surface, the method which comprises shaping one end of the stud with a point, contacting said point with said surface, and sending a current through said stud and said sufrace while applying thereto a percussive blow, said current initially melting the material of the contact area, thus separating the point from the surface and forming an arc whereupon said blow joins said end to said surface.

i. In the art of welding a loose stud to a comparatively larger surface, the method which comprises providing the stud with an end portion ap preciably reduced in cross section, pressing said end portion against said larger surface, and thereafter sending a current through said stud and said surface substantially simultaneously with applying thereto a percussive blow, whereby said current initially melts the region of the end 0 portion and the contacted surfaces to form an are between the stud and the surface as separated and ionized by the melting whereupon said blow joins said end portion and said surface.

5. In the art of welding a stud or wire to a surface, the method which comprises shaping one end of the stud with a substantially uneven surface, contacting said end with said surface, and sending through said stud and said surface, while applying thereto a percussive blow, a current sufficient initially to melt the material of the contact area, thus separating the end from the surface and forming an arc whereupon said blow joins said surfaces.

6. In the art of welding a stud or wire to a work surface, the method which comprises shaping one end of the stud with an, essentially uneven tip surface defining a contact cross section appreciably smaller than the cross section of the stud proper, contacting said tip surface with said work surface, sending a unidirectional current through said surfaces while pressurably contacting them, said current blow initially melting the material of the contact area, thus separating the two surfaces and forming an arc, and continuing said unidirectional current flow and pressurable contact until said surfaces are joined.

'7. In the art of welding a stud to a surface, the method which comprises shaping one end of the stud as a wire having a cross section appreciably smaller than that of the stud, contacting said wire with said surface, sending a unidirectional current through said Wire and said surface while pressurably contacting said wire and said surface, said current flow initially melting the material of the wire thus separating the wire from the surface and forming an arc, and continuing said unidirectional current flow and pressurable contact until said end and said surface are joined.

8. In the art of welding a stud to a surface, the method which comprises shaping one end of the stud with a point, contacting said point with said surface, sending a unidirectional current through said stud and said surface while pressurably contacting said point and said surface, said current flow initially melting the material of the contact area, thus separating the point from the surface and initiating an arc, and continuing said unidirectional current flow and pressurable contact until said end and said surface are joined.

9. In the art of welding a stud or wire to a surface, the method which comprises shaping one end of the stud with an edge, contacting said edge with said surface, sending a unidirectional current through said stud and said surface while pressurably contacting said edge and said surfaces, said current flow initially melting the material of the contact area, thus separating the edge from the surface and forming an arc, and continuing said unidirectional current flow and pressurable contact until said end and said surface are joined.

10. A method of welding which comprises, prepositioning a pair of metallic members with surfaces in contact, passing an electrical discharge from a condenser therebetween sufficient to produce a fluid condition of the members at the contacting surfaces, and applying a relatively sharp blow to at least one of the members such as to force said one member against the other member and force the contacting surfaces together between the peak and the end of the first pulse of the condenser discharge.

11. In a method of percussive welding electrically conductive members which comprises the steps of positioning the members with surfaces to be welded in contact, connecting a charged electrical condenser between the members so as to produce a sudden discharge of electrical energy between said surfaces, and striking one of the members a sharp blow to force it against the other member during the latter portion of the discharge of electrical energy between said surfaces to force the surfaces together.

12. The method of percussive welding which comprises, positioning a pair of metal members in engagement in substantially the position in which they are to be welded, passing a predetermined condenser discharge welding current impulse through the juncture of said members, and

10 applying a relatively sharp hammer blow to one of the members in a direction to force it toward the other member in predetermined timed relation to said impulse and during the firs pulse thereof to force said members together.

References Cited in the file of this patent UNITED STATES PATENTS N umber Name Date 1,339,967 Murray et al. May 11, 1920 1,608,825 Wagner Nov. 30, 1926 2,365,978 Murray Jan. 9, 1945 2,413,370 Palmer Dec, 31, 1946 2, il9,7-i9 Weinhardt Apr. 29, 1947 2,459,795 Dawson Jan. 25, 1 49 

